Vascular occlusion devices and methods

ABSTRACT

A vascular occlusion device includes a braided filament mesh structure defining a longitudinal axis. The mesh structure has a relaxed configuration in which it has an axial array of radially-extending occlusion regions, each of which has a proximal side and a distal side meeting at a peripheral edge, the sides of each occlusion region forming a first angle relative to the longitudinal axis. Each occlusion region is axially separated from the adjacent occlusion region by a reduced-diameter connecting region. The mesh structure is radially compressible to a compressed state in which it is deployed intravascularly to a target site through a catheter. Upon deployment, the device radially expands to a constrained configuration in which the peripheral edges of the occlusion regions engage the vascular wall, and the sides of the occlusion regions form a second angle relative to the longitudinal axis that is smaller than the first angle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) from U.S.Provisional Application No. 62/463,498; filed Feb. 24, 2017, and fromU.S. Provisional Application No. 62/507,641; filed May 17, 2017. Thedisclosures of both provisional applications, to the extent they are notinconsistent with the disclosure herein, are expressly incorporated byreference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

This disclosure relates to devices for closing a passageway in a body.The passageway may be a natural defect, one having occurred due todisease or trauma, or a healthy, but undesirable passageway. The subjectmatter of this disclosure includes methods for closing an opening intissue, a body lumen, blood vessel, a hollow organ, or other bodycavity. The disclosure also relates to occlusion devices and methods forminimally invasive implantation, in particular, percutaneousimplantation, of expandable braided occlusion devices for closingpassageways in the cardiovascular system.

The cardiovascular system is part of the larger circulatory system,which circulates fluids throughout the body. The circulatory systemincludes both the cardiovascular system and the lymphatic system. Thecardiovascular system moves blood throughout the body, and the lymphaticsystem moves lymph, which is a clear fluid that is similar to the plasmain blood. The cardiovascular system consists of the heart and bloodvessels (arteries, veins, and capillaries). It delivers oxygen andnutrients to the tissues and carries waste products to the organsresponsible for elimination. The arteries carry blood from the heart tothe rest of the body, and the veins carry blood back to the heart.

Initially open, and subsequently minimally invasive, surgical procedureswere used to occlude vessels and lumens, particularly when symptoms weresignificant and drug therapy inadequate. These techniques, althoughoften successful, were hampered by less than desirable morbidity andmortality rates, and many patients were excluded due to the severity andrisks associated with these procedures. In clinical practice today,occlusion devices are generally delivered, in a collapsed state,percutaneously with a catheter through leg or arm vessels to the targetvascular site or defect under fluoroscopic or ultrasonic guidance. Uponplacement at the target site, the devices are allowed to expand, insitu, to an expanded state for implantation. Reduced morbidity andmortality risks have been observed using these percutaneously-deliveredocclusion devices. Nevertheless, these devices may still suffer frompotential drawbacks, including navigation difficulty through thecatheter when collapsed, maintenance of device delivery flexibilitysufficient to reliably navigate blood vessels through small diameterintroducers, insufficient sealing of the vessel or defect, inadequatefixation of the device, subsequent reopening of initially occludedvessels, and inadequate provision for natural tissue ingrowth andhealing following implantation. These drawbacks and others provide theimpetus for the subject matter of this disclosure.

SUMMARY

Broadly, this disclosure relates to a medical device which, in someaspects, comprises an expandable mesh for at least partially closing avascular defect (e.g., a fistula), occluding or blocking leakage arounda previously-implanted vascular device, or closure of a healthy, butundesirable blood vessel or other bodily lumen.

In some aspects, a medical device in accordance with this disclosurecomprises an expandable tubular mesh structure for at least partiallyclosing a target site (e.g., a target vascular site), wherein theexpandable mesh is fabricated from a self-expanding filamentous braid(i.e., made of metallic wire or non-metallic fibers), formed into alinear array of flexible, reconfigurable disc-like mesh occlusionregions providing between 4 to 10 mesh layers per centimeter when thedevice is in an unconstrained, radially expanded configuration. When thedevice is deployed in the target site, the mesh occlusion regions arereconfigured within a linear distance that provides a short, focalocclusion between about 0.5 cm and 2.5 cm as measured between the mostdistal and most proximal occlusion regions.

In some aspects, a medical device, as described herein, comprises anexpandable tubular mesh structure for at least partially closing astructural vascular defect, wherein the expandable mesh structure isfabricated from self-expanding braid containing any of the materialsdescribed herein, resulting in a pore size of between about 0.05 mm and0.50 mm, such as between about 0.10 mm and 0.30 mm. Alternatively, poresizes in the range of about 0.10 mm to 2.0 mm may be employed. In someembodiments, the pore size may be in the range of 0.20 mm to 0.75 mm.

In some aspects, a medical device, as described herein, comprises anexpandable tubular mesh structure for at least partially closing abodily lumen, such as a blood vessel, fistula, aneurysm, a patent ductusarteriosus, the left atrial appendage of the heart, leakage paths aroundimplants (e.g. heart valves), or other vascular embolization targets,wherein the expandable mesh is fabricated from a tubular, self-expandingor shape-memory braided mesh structure.

In some aspects, a method is described for embolizing a target luminal(e.g., vascular) site by providing an expandable mesh structure that atleast partially occludes the site, wherein the device is over-sizeddiametrically, with respect to the site, by between about 10% and 150%.In some embodiments, the amount of over-sizing may be between about 25%and 75%.

In some aspects, a method is described for treating a vascular conditionby providing an expandable mesh structure that at least partiallyoccludes a target vascular site, such as an undesirable blood vessel,fistula, aneurysm, patent ductus arteriosus, the left atrial appendageof the heart, leakage paths around implants (e.g. heart valves), andother vascular embolization targets.

In some aspects, a method is described for treating a vascular site byproviding an expandable tubular mesh structure that at least partiallyoccludes the site, wherein the expandable mesh structure is fabricatedfrom a self-expanding mesh of braided fibers, filaments, or wirescontaining at least one of the following materials: nickel-titaniumalloys (e.g. Nitinol), stainless steel, alloys of cobalt-chrome,polyester, PTFE, ePTFE, TFE, polypropylene, nylon, TPE, PGA, PGLA, PLA,polyethylene (PE), high-density PE (HDPE), and ultra-high molecularweight PE (UHMWPE) (including oriented strands of UMHWPE commerciallyavailable under the tradenames “DYNEEMA” and “SPECTRA”).

In some aspects, a method is described for embolizing a target vascularsite, wherein the method includes delivering to the target site anexpandable mesh occlusion device, and allowing the device to expand toat least partially occlude the target site, wherein the expandable meshis fabricated from a self-expanding braided mesh with fiber diametersranging between about 0.013 mm and 0.080 mm.

In some aspects, a method is described for embolizing a blood vessel,wherein the method includes delivering to a target site in the vessel anexpandable mesh occlusion device, and allowing the device to expand sothat it at least partially occludes the vessel, wherein the expandablemesh is fabricated from a self-expanding braided mesh that allows thedevice to expand from a compressed state having an essentially linear ortubular configuration, to an expanded or relaxed state in which itassumes a radially-expanded state comprising a plurality ofaxially-spaced, radially-expanded occlusion regions, i.e., a lineararray of radially-expanded disc-like occlusion regions. In someembodiments, at least a portion of each of the occlusion regions formsan angle optimally between about 80° and 90° relative to thelongitudinal axis of the of the device when the device is notconstrained by the interior wall of the bodily lumen in which the deviceis deployed. This angle is decreased when the device is deployed andconstrained by the endoluminal wall. The occlusion regions may then havean axially-flattened state such that each disc forms a pair of conjoinedcones sharing a common base and defining a peripheral edge.

As used herein, the term “occlusion device,” unless otherwise limited,shall be construed to encompass any device that is implantable in abodily lumen for the purpose of at least partially obstructing thelumen, either by itself, or as an adjunct for embolization or tissueingrowth. The term “bodily lumen” shall be construed as encompassingblood vessels and any other organ or structure that has a lumen orpassageway that may provide a target site for occlusion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a portion of a human cardiovascularsystem, showing a typical arrangement for the intravascular delivery ofan implant, such as an occlusion device in accordance with thisdisclosure.

FIG. 2 is a simplified view of a device for the intravascular deliveryof an occlusion device in accordance with this disclosure, showing thedevice being deployed intravascularly.

FIG. 3 is an elevational view of an occlusion device in accordance withan embodiment of this disclosure.

FIG. 4 is an elevation view of the occlusion device of FIG. 3, showingthe device being delivered intravascularly to a target site.

FIG. 5 is a simplified view of a portion of an apparatus for braidingthe filament from which an occlusion device in accordance with aspectsof this disclosure is made.

FIG. 6 is a simplified view of the filamentous structure of an occlusiondevice in accordance with aspects of this disclosure.

FIG. 7 shows the process of flattening a filament used in themanufacture of an occlusion device in accordance with aspects of thisdisclosure.

FIG. 8 is an enlarged, detailed view of the filamentous structure of anocclusion device in accordance with aspects of this disclosure.

FIG. 9 is an elevation view of an occlusion device in accordance with anembodiment of this disclosure, showing the device deployed at a vascularsite.

FIG. 10 shows an embodiment of a heat treatment fixture formanufacturing an occlusion device in accordance with aspects of thisdisclosure.

FIG. 11 shows two envelopes of braid angles for braids of 0.019 mmdiameter NiTi wire with mandrels sized from 3.0 mm to 5.5 mm.

FIG. 12 shows two envelopes of braid angles for braids of 0.025 mmdiameter NiTi wire with mandrels sized from 5.5 mm to 8.0 mm.

DETAILED DESCRIPTION

Methods and apparatus are presented for the occlusion of bodily lumens,particularly vascular sites and vessels, by minimally invasiveimplantation, including percutaneous implantation of an expandableocclusion device. In some embodiments, the device may comprise aplurality of radially-expanded occlusion regions formed from a singletubular mesh structure, such as a braid of fine filaments (i.e., fibersor wires). In the treatment of vascular sites, the device may bedelivered to the site through an elongate tubular delivery device suchas a catheter or cannula, which may be inserted intravascularly througha blood vessel (such as the femoral vein or radial artery) and advancedto the target site. Typically, the device delivery and deploymentprocedure would be conducted under external imaging means such asfluoroscopy, x-ray, MRI or the like. Radiopaque markers may beincorporated into the occlusion device and/or the delivery device tohelp provide additional visibility under image guidance. Markermaterials may include, for example, tungsten, tantalum, platinum,palladium, gold, iridium or other suitable materials.

Occlusion devices in accordance with this disclosure are configured forintravascular delivery to a target site in a bodily lumen, particularlya vascular target site, by known techniques and procedures forintravascular deployment of vascular implants. In accordance withtypical procedures of this type, a guide wire 100 capable of traversingthe circulatory system is introduced into the patient through a vascularaccess site or puncture 102, as shown, for example, in FIG. 1. Forexample, an endoluminal vascular access site may be formed in a femoralartery or vein, iliac artery or vein or jugular artery or vein of apatient. This methodology of positioning a guide wire is known tophysicians skilled in the art of interventional therapy. Once the guidewire 100 is positioned, the vascular access site 102 is typicallydilated to permit entry of a delivery catheter 20 therethrough. Aprotective sheath (not shown) may be advanced to protect the vascularstructure. Thereafter, the guide wire 100 may be introduced into thepatient through the vascular access site 102 and advanced to the site ortarget of embolization. The delivery catheter 20 is then advanced overthe guidewire 100 until its distal end is situated adjacent the targetsite. Optionally, the delivery catheter 20 may be preceded by an outercatheter or “introducer” 22, as shown in FIG. 2, through which thedelivery catheter 20 is inserted. The introducer 22 may optionally beformed with a tapered distal end portion to assist in navigation throughvessels; alternatively, a flexible or removable dilator (not shown) maybe used, as is well-known. The delivery catheter 20 likewise can have atapered distal end portion.

Referring still to FIG. 2, an occlusion device 10, in accordance withthis disclosure, is structured, as described more fully below, so thatit may be resiliently compressed from a relaxed or expanded state to acompressed state for delivery, which is how the device is shown in FIG.2. In the compressed state, the device 10 may be substantially linear inconfiguration; that is, it resembles a cylinder or tube. The device 10is connected to the distal end of a pusher element 24 by a connectionelement (not shown) having a detachment mechanism, which may be of anysuitable type known in the art. The pusher element 24, typically in theform of, or comprising, a flexible wire, coil, multi-stranded helicalwire tube or rod, is introduced into the proximal end of the deliverycatheter 20 with the occlusion device 10 constrained in its compressedconfiguration, in which it is maintained by the constraint imposed bythe inner wall surface of the delivery catheter 20. With the device 10thus retained in a compressed state in the delivery catheter 20, it isadvanced through the delivery catheter 20 by means of the pusher element24 until it is at or near the target site in a bodily lumen, such as ablood vessel V (FIG. 2). At this point, the delivery catheter 20 ispulled proximally, freeing the occlusion device 10 from the constraintof the catheter 20, thereby allowing the occlusion device 10 to expandradially within the lumen so as to engage the endoluminal wall of theblood vessel V, as further described below, for deployment andimplantation at the target site. When the device 10 is deployed at thetarget site, it is detached from the pusher element 24 by operation ofthe detachment mechanism.

If an outer catheter or introducer 22 is used (as shown, for example, inFIG. 2), the introducer 22 is advanced intravascularly until its distalend near the target site. The delivery catheter 20 is advanced distallythrough the introducer 22 until the distal end of the delivery catheter20 is located at the target site. The device 10 is inserted into theproximal end of the delivery catheter 20 and pushed, by the pusherelement 24, along the length of the delivery catheter up to the distalend. The delivery catheter 20 is retracted, and the device 10 is urged(e.g., by the pusher element 24) out of the distal end of the deliverycatheter 20, thereby allowing the entire occlusive device 10 to expandto its functional size in an appropriate position for engagement withthe walls of the target vessel or lumen at the target site. Once thedevice 10 is properly positioned, it is detached by the user from thepusher element 24. In some embodiments, the detachment is accomplishedwith minimal (preferably zero or close to zero) force being imparted tothe device by the detachment mechanism to minimize movement of thedevice. In some embodiments, the occlusion device 10 is attached to thepusher element 24 by a tether (not shown), and the force applied neededfor detachment of the tether is preferably less than 1 newton, such as,for example, 0.2-0.8 newton. Once the device has been detached, thedelivery system may be withdrawn from the patient's vasculature orpatient's body.

Specific embodiments of the occlusion devices disclosed herein aredesigned for delivery through a small intravascular delivery catheter 20that preferably has an interior lumen diameter generally less than about0.7 mm, known in the art as a “microcatheter.” For the device to bedeliverable through the microcatheter, the collapsed profile or diameterof the device must be at least slightly less than the catheter lumen. Inaddition, the device must have sufficient flexibility, and sufficientlylittle outward radial force, to allow it to track through themicrocatheter without excessive friction or resistance. For a devicemade of braided filaments, these delivery constraints for microcatheterdeliverability limit the number and size of the filaments from which thebraided device is made. In addition, the number of filaments and theirdiameters dictate the pore structure of the device, which directlyimpacts how rapidly the device can occlude a vessel or lumen. Thefilaments and their resultant geometry in the formed structure of thedevice must provide sufficient strength and radial stiffness to providefor device stability when implanted to prevent distal migration and/orembolization downstream of the intended occlusion site. Accordingly,this disclosure describes the unique inter-relationships of thestructural parameters of the device which allow the braided meshstructure occlusion devices described herein to achieve the desireddelivery and performance characteristics.

An occlusion device in accordance with this disclosure advantageouslyhas three inter-related performance criteria: It must be deliverable tothe target site; it must remain at the target site (i.e., it does notmigrate and/or embolize downstream from the target site); and it must beocclusive within the target site.

Preferred deliverability characteristics are as follows:

Compressed Diameter (D_(P)) of the device is given by the equation:

D_(P)=√N_(W)*1.14*W/η, where N_(W) is the number of filaments formingthe device, W is the diameter of each filament, and n is the packingdensity of the constituent filaments.

The packing density for the filaments is the sum of the cross-sectionalareas of each wire relative to the area inside the perimeter of thepacked wires Collapsed tubular braided structures of round filamentshave been shown to have a packing density of about 0.75.

To be efficiently deliverable through a microcatheter of inside diameterD_(C), the device must meet the following condition:

(D_(P)+2*T_(H))<D_(C), where T_(H) is the wall thickness of the devicehub, as described below.

The friction of the device passing through the microcatheter isproportional to S_(r) and to N_(F), where S_(r) is the radial stiffnessof each surface feature of the braided wire portion the device, andN_(F) is the number of surface features of the radially-expandedocclusion portions of the device, as described below.

The radial stiffness S_(r), in turn, is proportional to N_(W) and W⁴,and it is positively correlated to α and 1/R_(E), where α is the braidor pick angle (as described below), and R_(E) is the edge radius of eachradially-expanded occlusion region, as described below.

It is also assumed that the braid or pick angle α=F(W, N_(W), D_(b)),where D_(b) is the diameter of the mandrel on which the mesh structureis formed, as explained below.

The change in braid angle α for a change in braid length, B may beexpressed as:

α_(n)=cos−1((B_(n)/B_(i)) cos α_(i)), where i indicates the initialvalue and n is a subsequent value

These parameters drive all of the resulting device performanceparameters. The goal is to use as many wires of the largest diameterpossible to construct a vascular occlusion device that is occlusive andstable, while being deliverable through a microcatheter sizedappropriately for the anatomical structures of concern in a particularpatient.

In some embodiments, to achieve the balance of the key parameters, atubular braided wire mesh structure is formed on a mandrel using alow-tension braiding system as described herein, and the braidingparameters are set to obtain a braid or pick angle a in a particularrange for a given wire diameter and mandrel diameter. In someembodiments, the braid angle will be within a preferred envelope a shownin FIGS. 11 and 12. FIG. 11 shows the two preferred envelopes (A and B)of braid angles for braids of 0.019 mm (0.00075″) diameter NiTi wire forvarious mandrels sized from 3.0 mm to 5.5 mm. FIG. 12 shows the twopreferred envelopes (C and D) of braid angles for braids of 0.025 mm(0.001″) diameter NiTi wire with various mandrels sized from 5.5 mm to8.0 mm. After initial forming, the braid may be secondarily formed,typically by heat treatment described herein, into a final form. In oneembodiment, a braided comprising a plurality of wires with an averagediameter of between about 0.017 mm and 0.021 mm, formed into a tubularmesh structure having a braid angle that lies within envelope A, canthen be formed into an occlusion device with a plurality of disc-likeocclusion regions, wherein the device will have both the desirableradial stiffness and the necessary deliverability through amicrocatheter. In another embodiment, a braided mesh comprising aplurality of wires, each with an average diameter of between about 0.022mm and 0.028 mm, formed into a tubular braided mesh structure having abraid angle that lies within envelope C, can then be formed into anocclusion device with a plurality of radially-expanded, disc-likeocclusion regions, wherein the device will have both the desirableradial stiffness and the necessary deliverability through a catheter ofa given internal diameter.

As shown in FIG. 3, an occlusion device 10 in accordance with anexemplary embodiment of this disclosure comprises a tubular braidedstructure, which has, in a relaxed or expanded state, a plurality ofradially-expanded and thus radially extending occlusion regions 12,which, in some embodiments, are disc-like in configuration, as mentionedabove. The occlusion regions 12 are axially spaced along the length ofthe device; that is, the device comprises a linear array of suchocclusion regions 12. Each radially extending occlusion region 12(hereinafter “disc,” solely for the sake of brevity, and not in anylimiting way) is separated from the nearest adjacent radially extendingdisc 12 by a tubular braided connecting region or core section 14 ofreduced radius relative to the occlusion regions 12. The core sections14 separate each adjacent pair of discs 12 by a core length that isadvantageously less than about 3.0 mm, such as, for example, betweenabout 0.5 mm and 2.5 mm.

As shown in FIG. 3, the device 10 defines a longitudinal axis X betweena distal end (on the left side of the drawing) and a proximal end (onthe right side of the drawing). The braided mesh structure is gatheredtogether at each of the proximal and distal ends, where the filaments ofthe mesh are terminated in and retained by a proximal hub 26 and adistal hub 28, respectively. An attachment fixture 29 may advantageouslybe fixed to, or be integral with, the proximal hub 26, for detachableconnection to a pusher element 24 by a detachment mechanism, which mayadvantageously include a detachable tether (not shown), as mentionedabove.

Each disc 12 may advantageously be configured with a rounded peripheraledge or “apex” 16, the apices 16 of successive discs 12 being separatedby a distance that may be referred to as a “pitch,” as with screwthreads. In some embodiments, the final, as-formed occlusive device 10in its relaxed state may define a plurality of discs 12 with a spacingor pitch (apex to apex) distance, as shown in FIG. 3, between about 0.5mm to 5 mm, such as, for example, between about 0.7 mm and 4.5 mm.

Referring still to FIG. 3, in the relaxed or radially-expanded state ofthe device 10, each disc includes a proximal or trailing side 17 and adistal or leading side 19, meeting at the peripheral edge or apex 16. Afirst disc angle θ₁ is defined between either the proximal side 17 orthe distal side 19 of each radially-extending disc 12 and thelongitudinal axis X. When the device 10 is in its relaxed or expandedstate, the angle θ₁ may advantageously be between 70° and 90°, althoughsmaller angles (e.g., not greater than 85°) may be satisfactory in someembodiments, depending on the application. The disc angle decreases to asecond disc angle θ₂ that is smaller than the first disc angle θ₁ whenthe device is partially constrained owing to the engagement of theperipheral edges 16 of the discs 12 with an endoluminal wall upondeployment of the device in a bodily lumen, as shown in FIG. 4. Thesecond disc angle θ₂ may be as small as 25°, although it may bebeneficial for the second disc angle θ₂ to be up to about 70°, as alarger angle makes the total occlusion length or “landing zone” smalleror more compact, and thus allows the physician to keep the occlusionmore focal at desired location. In addition, the more compact the deviceand the closer the radially extending discs are to each other, the moreefficiently the device may work, thereby achieving occlusion morerapidly due to subsequent layers of filament acting on the flow of bloodbefore the flow has returned to laminar flow after being disrupted andslowed by an initial mesh layer.

The effective size of the braid may be reduced as blood passes througheach layer of mesh. The pore size of the initial layer ranges between 50microns and 500 microns. Effective pore sizes may be reduced with eachsubsequent layer.

The radially-extending discs 12 can have a variety of shapes withvarious radial cross-sections, including, but not limited to, circular(as shown), ovoid, rectangular, diamond, or arbitrarily-shaped. Inaddition, the discs 12 can have generally the same diameter (as shown),or different diameters. They may have similar thicknesses and spacingbetween them, or varied thicknesses and spacing between them. In someembodiments, the disc diameters are more than about five times theirthickness at the thickest point when unconstrained. The occlusion device10 may comprise between 2 and 8 discs in some embodiments, such as, forexample, 3 to 5 discs. Each disc 12 may comprise two layers (meshstructures), that generally conform to the cross-section of the vesselor embolization site, thus spanning the lumen with a microporous flowdisruptor. In some embodiments, narrow and tightly spaced discs mayprovide for a large number of mesh layers in close proximity, which mayoffer improved hemostasis. In some embodiments, when unconstrained, theocclusion device may comprise from 6 and 12 layers of mesh (each disccomprising two layers) in a linear distance of less than about 10 mm,and in less than about 25 mm in other embodiments. In some embodiments,the ratio of the linear distance between the discs and the largest discdiameter may be between about 0.7 and 2. In some embodiments, the deviceprovides at least about 4 mesh layers per centimeter and in someembodiments, it provides from 4 to 10 mesh layers per centimeter.Optionally, the smaller diameter portions of the braid that extend fromthe proximal and distal discs, and that form the core portions 14 ofbraid between discs 12, may have a substantially uniform cylindricalshape; alternatively, the core portions 14 may have different diameters.

A short, more focal occlusion can be beneficial by keeping the occlusionzone away from branch vessels in which occlusion is not desired. In someembodiments, the device may provide a high density of mesh layers thateach define a second disc angle θ₂ relative to the longitudinal axis Xof the occlusion device 10 that is between about 25° and 70°, preferablybetween 40° and 60°, when the device assumes its partially constrainedconfiguration upon deployment at the target site, as noted above. Insome embodiments the second disc angle θ₂ (in the partially constrainedstate upon deployment) may be smaller than the first disc angle θ₁ (inthe relaxed or expanded state) by about 20° to 60° implanted state.

When the device 10 is deployed (implanted) at the target site, each ofthe discs 12 may create short, substantially circular contact regionsbetween the peripheral edge 16 and the vessel wall, as shown in FIG. 4.Accordingly, the device 10 may provide a plurality of short and closelyspaced substantially circular contact regions. In some embodiments, forexample, there may be between 3 and 7 such contact regions within alinear distance of between about 1 cm and 3 cm within the blood vessel,preferably less than about 2.5 cm. In some embodiments, for example,there may be 2-4 contact regions per cm. The substantially circularcontact regions are defined by the thickness of the peripheral edge 16of each disc 12, typically less than about 2 mm, and preferably lessthan about 1 mm, corresponding to very short lengths along thelongitudinal axis X. When the device 10 is implanted in a bodily lumen,as shown in FIG. 4, an occlusion zone Z in the lumen may be defined asthe length of the lumen between the most distal and the most proximalocclusion discs 12 (as measured between their respective peripheraledges 16). Because of the small size of the contact regions (as definedabove) relative to the length of the occlusion zone Z, when the device10 is implanted, only a relatively small portion of the surface area ofthe occlusion zone Z is contacted by the device. In some embodiments,for example, the surface area of contact is less than about 25% of thetotal surface area of the occlusion zone Z. The total occlusion zoneprovided by the device 10 within a vessel is thus shorter and more focalthan has heretofore been the norm, thereby yielding the aforementionedadvantage over devices that provide relatively long occlusion zones andlarge vessel contact areas.

One or both of the sides of any or all of the discs may be concave orconvex. In some embodiments, as shown in FIG. 9, one or more discs 12′may comprise a concavity 31 formed into a cup-like shape that facesdownstream, so that blood flow and pressure in the vascular site to beembolized tends to increase the outward force against the vessel thatmay enhance the friction force holding the device in place, andtherefore improve its stability and reduce the risk of downstreammovement of the device. Alternatively, the discs may have a simpleplanar structure or have a small angulation so that they are thicker atthe base than at the apex 16, as shown in FIG. 3. Disc and core portiondiameters, shapes and dimensions vary to cover the wide range of defectsizes and shapes. In some embodiments the disc diameter may rangebetween 2 mm and 12 mm, and the core portion diameter may range between0.25 mm and 3 mm.

As shown in FIG. 3, in some embodiments, the peripheral edges or apices16 of the radially-extending discs 12 of the occlusion device mayadvantageously have an edge radius R_(E) of between about 0.10 mm and0.40 mm. The core portions 14 between adjacent discs may advantageouslydefine a core radius of Rc of between about 0.25 mm and 1.0 mm. Thesespecific ranges of disc edge and core radii for the occlusion device mayprovide a heretofore unknown desirable balance of deliverability andmaintenance of the close spacing of the discs. Smaller radii increasethe force required for delivery through a microcatheter that may benecessary for treatment of tortuous and small vessel targets.Conversely, larger disc edge radii, in particular, may result in alonger implant and less focal occlusion when implanted. A shorter deviceand more focal occlusion are generally desirable to the user(physician). Further, larger spacing of the discs may result in longerocclusion times.

In any of the embodiments described herein, the device components maycomprise a mesh of wires, filaments, threads, sutures, fibers or thelike (herein called “filaments 30”) that have been configured to form aporous fabric or structure. The filaments 30 may be constructed usingmetals, polymers, composites, and/or biologic materials. Polymermaterials may also include polymers such as polyester, polypropylene,nylon, PTFE, ePTFE, TFE, PET, TPE, PGA, PGLA, or PLA. Other suitablematerials known in the art of elastic implants may be used. Metallicmaterials may include, but are not limited to, nickel-titanium alloys(e.g. Nitinol), platinum, cobalt-chrome alloys such as Elgiloy,stainless steel, tungsten, or titanium.

In some cases, the specific construction of a drawn filled tube wire orfilament may be important to enhance the external visualization and/ormaintain desired performance characteristics of the occlusion device.More specifically, it may be important to balance the stiffness,elasticity and radiopacity of the composition. In particular, for drawnfilled tube filament embodiments that include an internal wire ofductile radiopaque material, such as platinum, and an outer tube of anelastic or super-elastic material such as NiTi, it can be necessary (orat least advantageous) to balance the ratio of the percentcross-sectional area of the internal wire with regard to the overallcross-sectional area of the filament. Such a ratio may be referred to asa “fill ratio.” If an embodiment includes too little radiopaque internaltube material relative to the external tube material, there may not besufficient radiopacity and visibility. On the other hand, if anembodiment includes too much internal wire material with respect to theelastic external tube, the mechanical properties of the ductileradiopaque material may overwhelm the elastic properties of the outertube material, and the filaments may be prone to taking a set aftercompression, etc., resulting in permanent deformation. For someembodiments, a desired composite or drawn filled tube filament may beconstructed with a fill ratio of cross-sectional area of internal fillwire to cross-sectional area of the entire composite filament of betweenabout 10% and about 50%, more specifically between about 20% and about40%, and even more specifically, between about 25% and about 35%.

In some embodiments, the devices for treatment of a patient'svasculature may have at least about 25% composite filaments relative tothe total number of filaments, and in some embodiments such devices mayhave at least about 40% composite filaments relative to a total numberof filaments in the device. For example, a first subset of elongateresilient filaments may comprise composite materials, each having acombination of highly radiopaque material and a high strength material,and a second subset of elongate resilient filaments may comprise mostlya high strength material. For example, the highly radiopaque materialmay comprise platinum, platinum alloy such as 90% platinum/10% iridium,or gold, or tantalum. The high strength material may comprise NiTi.While composite wires may provide enhanced visualization and/ormechanical characteristics, they may, in some configurations, havereduced tensile strength in comparison to NiTi wires of a similardiameter. In other configurations, depending on their diameter, thecomposite wires may increase the collapsed or compressed profile of thedevices. Therefore, it may be beneficial to minimize the number ofcomposite wires. Lower percentages of composite wires may not besufficiently visible with current imaging equipment, particularly inneurovascular applications where the imaging is done through the skull.In addition, too many composite wires (or composite wires with extremelyhigh fill ratios) may result in devices with excessive artifact on CT orMRI imaging. The described ratios and amounts of highly radiopaquematerial provide a unique situation for neurovascular implants where theperiphery of the device is just visible under transcranial fluoroscopy,but the device imaged area is not completely obliterated (i.e., due toan artifact), as it is with conventional embolic coils that are madesubstantially out of platinum or platinum alloys. One manner ofachieving the desired degree of radiopacity is by selecting a particularcombination of fill ratio of the composite filaments and the percent ofcomposite filaments in relation to the total number of wires. The totalpercent of radiopaque platinum, for example, in the braided structuremay be between about 15% and 30%.

In any of the braid filaments described herein, the cross-section may becircular, ovoid, rectangular or square. In some embodiments, thefilaments 30 may be formed initially with a circular cross-section, andthen rolled or partially flattened to form a flattened filament 30′having a generally rectangular cross-section with rounded corners, asshown in FIG. 7. This configuration may provide improved ability tobraid the desired configuration of braid angle and pore structure.

Specifically, for a given filament thickness, the larger the “picklength” (distance between filament crossings), the longer the beamlength relative to the filament displacement, and the lower the stressin the filament induced by the displacement. Also, for a given picklength, the smaller the filament thickness, the larger the pick length,and the longer the beam length relative to the filament displacement,the lower the stress in the filament induced by the displacement. If acircular filament is subsequently flattened along its axis, forming twoparallel planes symmetric about the filament axis, then the filamentthickness will be reduced without reducing the cross-section and thusthe tensile strength of the filament.

Flattening the filament requires less beam displacement to form thebraid. Therefore, one can expect smaller pick length for a givenfilament tension. Accordingly, reducing pick length reduces the “pore”size of the weave. Also, the flattened filament is “wider” than thediameter of the circular filament, and as such, occupies more of thepore surface area for any equal pick length, further reducing pore size.

Bending stiffness is E*I, where E is the tensile modulus, and I is thepolar moment of inertia of the cross-section normal to the bending axis.E is the same for both flattened (elliptical) and circular filaments.The value of I of the flattened filament is 22% that of the circularfilament of the same cross-sectional area. Therefore, the flattenedfilament is only 22% as stiff. Under the same tensile load, the picklength would be reduced based on this factor alone. Flattening acircular filament will reduce the braided pore size due to smallerbending displacement, wider cross-section, and reduced bendingstiffness.

In some embodiments, the device may comprise a braided mesh of finefilaments. In some embodiments, the braided mesh may be formed over amandrel 40, as is known in the art of tubular braid manufacturing andshown in FIG. 5. The mesh is formed with a braid angle a relative thelongitudinal axis Y of the mandrel 40. The braid angle a may becontrolled by various means known in the art of filament braiding. Thebraids for the mesh components may have a generally constant braid anglea over the length of a component, or the braid angle a may be varied toprovide different zones of pore size and radial stiffness. The “poresize” is defined as the largest circle that may be inscribed inside thediamond formed by the crossed filaments, as indicated by the dashedcircle P in FIG. 8.

In some embodiments, as shown in FIG. 6, substantially non-structuralfilamentary or fibrous members 32 may be attached or interwoven into thestructural filaments 30 of a portion of the device to increase aresistance to the flow of blood through the mesh structure or enhancethe formation of thrombus and/or healing of the tissue around thedevice. In some embodiments, one or more fibers or yarns 32 may beinterwoven or interlaced into the braided mesh, as shown in FIG. 6. Thenon-structural fibers 32 may be interlaced into the braided mesh duringthe braiding process or after. The non-structural fibers 32, which maybe microfibers or any other suitable fibers, may be polymeric and maybeneficially be more thrombogenic than the mesh filaments. Thenon-structural fibers 32 may include, but are not limited to, any of thematerials described herein.

In some embodiments, the tubular braided filament mesh structure can beformed by a braiding machine. It may be advantageous to utilize abraiding machine that does not employ bobbins or other filament spoolingand tensioning mechanisms, typical of many conventional braiders, asthey make braiding of very fine filaments and mixing of differentfilament diameters more difficult. Low tension braiding machines canallow less filament breakage and are more amenable to mixed diameterfilament braid. In some embodiments, the braided filament mesh structurecan be braided using methods or devices described in one or more of:U.S. Pat. No. 8,833,224, entitled “BRAIDING MECHANISM AND METHOD OFUSE”; U.S. Pat. No. 8,826,791, entitled “BRAIDING MECHANISM AND METHODOF USE”; U.S. Pat. No. 8,261,648, entitled “BRAIDING MECHANISM ANDMETHOD OF USE”; U.S. Pat. No. 8,820,207, entitled “BRAIDING MECHANISMAND METHOD OF USE”; and U.S. Patent Publication No. 2014/0318354,entitled “BRAIDING MECHANISM AND METHOD OF USE”. The disclosures of allof the aforementioned patents are hereby incorporated by referenceherein.

The tubular braided mesh may then be further shaped using a heat settingprocess. As is known in the art of heat setting nitinol wires, afixture, mandrel or mold may be used to hold the braided tubularstructure in its desired configuration, then subjected to an appropriateheat treatment, such that the resilient filaments of the braided tubularmember assume or are otherwise shape-set to the outer contour of themandrel or mold. A conventional heat treatment fixture 50 is shown inFIG. 10, in which a mesh device or component 10 is held. The fixture 50is configured to hold the device or component in a desired shape, andthe device or component is heated while so held to about 475-525° C. forabout 5-30 minutes to shape-set the structure. The heat setting processmay be performed in an oven or fluidized bed, as is well-known. In someembodiments, the heat setting process may be done in an inert gasenvironment. In some embodiments, a system for heat treating a devicecomprises a chamber configured to contain bath media, a container withinthe chamber and configured to hold the device, an air inlet gate fluidlyupstream of the chamber and configured to be coupled to a gas source toflow gas into the chamber to fluidize the bath media, and a heatingelement between the air inlet gate and the chamber. The bath media mayadvantageously and optionally include sand. The gas source may compriseair, nitrogen, hydrogen, carbon monoxide, or any combination thereof.The system may further comprise thermal sensors electrically connectedto a temperature regulator. In some embodiments, a system for heattreating a device comprises a chamber configured to contain bath media,and a container within the chamber and configured to hold the device.Gas flow into the chamber is provided so as to fluidize the bath media.

In some embodiments, the device can be formed at least in part from acylindrical braid of elastic filaments. Thus, the braid may be radiallyconstrained without plastic deformation and will self-expand on releaseof the radial constraint. Such a braid of elastic filaments is hereinreferred to as a “self-expanding braid.” In accordance with the presentdisclosure, braids of generally smaller filaments than current occlusiondevices are preferably used. In some embodiments, the thickness of thebraid filaments would be less than about 0.10 mm. In some embodiments,the braid may be fabricated from wires with diameters ranging from about0.015 mm to about 0.080 mm.

In some embodiments, the diameter of the braid filaments can be lessthan about 0.5 mm. In other embodiments, the filament diameter may rangefrom about 0.01 mm to about 0.40 mm. In some embodiments, braidfilaments of varying diameters may be combined in the mesh to impartdifferent characteristics including, e.g., stiffness, elasticity,structure, radial force, pore size, occlusive ability, and/or otherfeatures. In some embodiments, larger, structural filaments may befabricated from wires with diameters ranging from about 0.025 mm toabout 0.25 mm. In some embodiments, the thickness of the smaller braidfilaments would be between about 0.01 mm about 0.05 mm. The ratio of thenumber of small filaments to the number of large filaments may bebetween about 2 and 20, such as, for example, between 4 and 12. Anexemplary embodiment comprising filaments of two different sizes(cross-sectional areas) is shown, for example, in FIG. 8, in which anarray of larger filaments 30L is integrated into an array of smallerfilaments 30S.

Prior to treatment, a device size is chosen based on the size andmorphology of the site to be embolized. In general, the device isgenerally selected so that the diameter of its occlusion regions in theexpanded state is larger than the diameter or largest dimension of thesite, and, thus over-sized, provides a residual radial force, lendingstability to the device. When deployed in a vascular site in anover-sized and at least partially compressed state, the device willassume a constrained configuration, in which the shape of the discs 12will be axially elongated as compared to the expanded or relaxed stateof the device, thereby decreasing the disc angle relative to thelongitudinal axis of the device, as described above. The device may beover-sized diametrically relative to the target vessel diameter bybetween about 10% and 100% in some embodiments, and preferably betweenabout 25% and 75%. When deployed in an over-sized and thus partiallycompressed state, the discs assume a constrained configuration, forminga plurality of mesh layers (i.e., two for each disc 12), in which atleast a portion of the external surface of each disc 12 forms theaforementioned second disc angle θ₂ with respect to the longitudinalaxis X of the device (which will generally correspond with the locallongitudinal axis of the vascular site, e.g. blood vessel). As mentionedabove, the second disc angle θ₂ will typically be measurably smallerthan 70°, such as, for example, between about 40° and 60° relative tothe longitudinal axis X of the device. In some embodiments, the device10 has a plurality of layers packed or configured within a lineardistance that provides a short, focal occlusion zone Z of less thanabout 2.5 cm in length, such as, for example, between about 0.5 cm and2.0 cm, as measured between the apices 16 of the most distal and mostproximal discs 12 when the occlusion device is implanted, as shown inFIG. 4.

The shape and porosity of the device work synergistically to providevascular occlusion and a biocompatible scaffold to promote new tissueingrowth. These functions can be influenced by the “pore size” or “weavedensity” generally described as the pick count (number of interlacings)per unit length of the material. The devices in accordance with thepresent disclosure provide generally higher wire counts than currentocclusion devices and thus smaller pore sizes, yielding improvedocclusion performance, and thus may obviate the need for polymer fabriccomponents that can increase thromboembolic risk due to clot formation,while also increasing the collapsed profile or diameter of the device.Pore sizes in the range of about 0.05 mm to 0.50 mm may be utilized. Insome embodiments, the pore size may be in the range of 0.10 mm to 0.25mm. The relatively higher wire counts provide a large number of filamentor wire radial traverses of the target vessel that is being occluded.Since each disc provides two filament radial traverses from the centralcore portion to the apex of the disc, the total number of wire radialtraverses in a device is equal to the number of filaments or wire timesthe number of discs times 2. In some embodiments, each radiallyextending occlusion region or disc defines two radial traverses for eachwire, wherein the total number of radial traverses for the device isbetween 720 and 2000.

In any of the embodiments herein, the device 10 may contain at least onetine, barb, hook, pin or anchor (hereinafter called “barbs”, not shown)that may be incorporated into the structure to help provide additionalfixation of the device to the vessel wall or other tissue. The length ofthe barbs may be from about 0.25 to 3 mm, and preferably between about0.5 to 2 mm.

Optionally, the occlusion device may be constructed to provide theelution or delivery of one or more beneficial drugs and/or otherbioactive substances into the blood or the surrounding tissue.Optionally, the device may be coated with various polymers to enhanceits performance, fixation, and/or biocompatibility. Optionally, thedevice may incorporate cells and/or other biologic material to promotefixation, sealing, reduction of leaks or healing. In any of the aboveembodiments, the device may include a drug or bioactive agent to enhancethe performance of the device and/or healing of the target site andnearby tissue. In some embodiments, at least a portion of the device mayinclude: an antiplatelet agent, including but not limited to aspirin;glycoprotein IIb/IIIa receptor inhibitors (including one or more ofabciximab, eptifibatide, tirofiban, lamifiban, fradafiban, cromafiban,toxifiban, XV454, lefradafiban, klerval, lotrafiban, orbofiban, andxemilofiban), dipyridamole, apo-dipyridamole, persantine, prostacyclin,ticlopidine, clopidogrel, cromafiban, cilostazol, and/or nitric oxide.In any of the above embodiments, the device may include ananticoagulant, such as heparin, low molecular weight heparin, hirudin,warfarin, bivalirudin, hirudin, argatroban, forskolin, ximelagatran,vapiprost, prostacyclin and prostacyclin analogues, dextran, syntheticantithrombin, Vasoflux, argatroban, efegatran, tick anticoagulantpeptide, Ppack, HMG-CoA reductase inhibitors, and thromboxane A2receptor inhibitors. Device embodiments herein may include a surfacetreatment or coating on a portion, side surface, or all surfaces,wherein the surface treatment or coating promotes or inhibitsthrombosis, clotting, healing or other embolization performancemeasures. The surface treatment or coating may be a synthetic, biologicor combination thereof. For some embodiments, at least a portion of asurface of the device may have a surface treatment or coating made of abiodegradable or bioresorbable material such as a polylactide,polyglycolide or a copolymer thereof. Another surface treatment orcoating material which may enhance the embolization performance of adevice includes a polysaccharide, such as an alginate-based material.Some coating embodiments may include extracellular matrix proteins suchas ECM proteins. One example of such a coating may be Finale Prohealingcoating which is commercially available from Surmodics Inc., EdenPrairie, Minn. Another exemplary coating may be Polyzene-F, which iscommercially available from CeloNovo BioSciences, Inc., Newnan, Ga. Insome embodiments, the coatings may be applied with a thickness that isless than about 25% of a transverse dimension of the filaments.

The terms “formed”, “preformed” and “fabricated” may include the use ofmolds or tools that are designed to impart a shape, geometry, bend,curve, slit, serration, scallop, void, hole in the elastic,super-elastic, or shape memory material or materials used in thecomponents of the device. These molds or tools may impart such featuresat prescribed temperatures or heat treatments.

An exemplary low force detachment system may comprise a mechanism fordeploying an occlusion device in accordance with this disclosure as animplant in a bodily lumen, wherein the implant is delivered to a luminalsite through a catheter by means of a pusher implement having a distalend to which a proximal end of the implant is detachably connected by afilamentous tether (not shown). The tether extends from a first end,through a “fenestration feature” (e.g., an eyelet or a loop) on theproximal end of the device, to a second end. The first end of the tetheris connected to a tether take-up assembly in a tether control device,and the second end of the tether is releasably captured in the tethercontrol device by a tether retention assembly that is operable torelease the second end when the device is deployed. Upon release of thesecond end by the retention assembly, the take-up assembly withdraws thetether through the fenestration feature until the tether is free of thefenestration feature. The system may preferably detach the deviceinstantaneously or nearly so, that is, in less than about 1 second. Thesystem may preferably detach the device by mechanical means, but withoutthe transmission of torque in or through the delivery catheter orpusher. In some embodiments, the system may comprise an interlockingloops detachment system where a user can disengage an occlusion devicethrough a single action on the retraction device that preferably, onlyacts on the implant pusher guidewire during a retraction phase ofmovement, and allows for resetting of the retraction device forretraction without reinsertion of the guidewire. In one embodiment, thesystem may comprise an implant comprising a proximal end and a distalend with a first loop attached at its proximal end; a sheath comprisinga proximal end and a distal end with a second loop attached near itsdistal end; a guidewire slidably disposed within the sheath having aproximal end and distal end; wherein the guidewire, when engaged throughthe first and second loops provides a releasable connection of theimplant to the sheath that can be released by retraction of theguidewire; a handle handpiece comprising a retraction mechanism adaptedto receive the proximal ends of the sheath and guidewire; the retractionmechanism comprising a finger actuator, a ratcheting device, a firstspring member and second spring member; the ratcheting device comprisinga rotatable lever, a gripping insert, an anvil, a guide arm and a guideramp; wherein the first spring member biases the rotatable lever againstthe guidewire and the second spring member provides a biasing forceagainst retraction of the finger actuator; wherein the gripping insert,when actuated by the finger actuator, acts on the guidewire to retractthe guidewire within the sheath and release the implant.

For some embodiments, the detachment of the device from the deliveryapparatus of the delivery system may be effected by the delivery ofenergy (e.g., electrical current, heat, radiofrequency, ultrasound,vibrational, or laser) to a junction or release mechanism between thedevice and the delivery apparatus.

Disclosed herein is a detailed description of various illustratedembodiments of the disclosed subject matter. This description is not tobe taken in a limiting sense, but is made merely for the purpose ofillustration of the general principles of such subject matter. Furtherfeatures and advantages of the subject matter of this disclosure willbecome apparent to those of skill in the art in view of the descriptionof embodiments disclosed, when considered together with the attacheddrawings.

Although several embodiments of the subject matter of this disclosurehave been described in terms of particular embodiments and applications,one of ordinary skill in the art, in light of this teaching, cangenerate additional embodiments and modifications without departing fromthe spirit of or exceeding the scope of the disclosure. Accordingly, itis to be understood that the drawings and descriptions herein areproffered by way of example to facilitate comprehension of thedisclosure and should not be construed to limit the scope thereof.

1. A device for occluding a bodily lumen, comprising: a mesh structurecomprising a plurality of braided filaments, the mesh structure defininga longitudinal axis extending between a proximal end and a distal end,the filaments of the mesh structure being fixed in a proximal hub at theproximal end and in a distal hub at the distal end; wherein the meshstructure is radially compressible from a fully-expanded relaxedconfiguration to a compressed configuration, and is resilientlyexpandable from the compressed configuration to a partially-expanded,constrained configuration when deployed in the lumen; wherein the meshstructure in the relaxed configuration includes a plurality of radiallyextending occlusion regions spaced along the longitudinal axis, each ofthe occlusion regions having a side defining an angle of 70° to 85°relative to the longitudinal axis of the structure; and wherein, in theconstrained configuration of the mesh structure, each radially extendingocclusion region defines two radial traverses of the lumen for eachfilament, wherein the total number of radial traverses is between 720and
 2000. 2. The device of claim 1, wherein the mesh structure is asingle layer continuous tubular braided structure.
 3. The device ofclaim 1, wherein each radially extending occlusion region has a firstdiameter and is separated from the nearest adjacent radially extendingocclusion region by a connecting portion of the mesh structure having asecond diameter less than the first diameter.
 4. The device of claim 1,wherein the mesh structure in the relaxed configuration comprises atleast three radially extending occlusion regions.
 5. The device of claim1, wherein the mesh structure defines an axial length along thelongitudinal axis, and wherein the occlusion regions provide between 4and 10 mesh layers per centimeter of the axial length.
 6. The device ofclaim 1, wherein the angle when the mesh structure is in the constrainedconfiguration is smaller than the angle when the mesh structure is inthe relaxed configuration.
 7. The device of claim 1, wherein each of theocclusion regions has a peripheral edge at which each of the occlusionregions has a thickness of not more than about 2 mm.
 8. The device ofclaim 7, wherein the device has an axial length along the longitudinalaxis, and wherein the device comprises between three and seven radiallyextending occlusion regions, whereby the device includes between threeand seven peripheral edges per centimeter of the axial length.
 9. Adevice for occluding a bodily lumen, comprising: a mesh structuredefining an axial length along a longitudinal axis between a proximalend and a distal end, the mesh structure comprising a braided filamentmesh extending between the proximal end and the distal end, the braidedfilament mesh comprising a plurality of braided filaments terminating atthe proximal end in a proximal hub and at the distal end in a distalhub; wherein the mesh structure has a radially compressed configurationand a radially expanded relaxed configuration; wherein the meshstructure in the relaxed configuration has a plurality of radiallyextending occlusion regions having a first diameter spaced from eachother along the longitudinal axis, each radially extending occlusionregion being axially separated from the nearest adjacent radiallyextending occlusion region by a connecting region having a seconddiameter less than the first diameter, each radially extending occlusionregion having a proximal side and a distal side meeting at a peripheraledge; and wherein the occlusion regions provide between 4 and 10 meshlayers per centimeter of the axial length.
 10. The device of claim 9,wherein the mesh structure is a single layer continuous braidedstructure.
 11. The device of claim 9, wherein the mesh structure in therelaxed configuration has at least three radially extending occlusionregions.
 12. The device of claim 9, wherein at least one of the proximalside and the distal side defines an angle of between 70° and 85°relative to the longitudinal axis in the relaxed configuration.
 13. Thedevice of claim 9, wherein the mesh structure assumes apartially-expanded constrained configuration within the bodily lumen,whereby, in the constrained configuration, each radially extendingocclusion region defines two radial traverses of the lumen for eachfilament, wherein the total number of radial traverses is between 720and
 2000. 14. The device of claim 9, wherein the mesh structure assumesa partially-expanded constrained configuration within the bodily lumen,and wherein the angle when the mesh structure is in the constrainedconfiguration is smaller than the angle when the mesh structure is inthe relaxed configuration.
 15. The device of claim 9, wherein each ofthe occlusion regions has a peripheral edge at which each of theocclusion regions has a thickness of not more than about 2 mm.
 16. Thedevice of claim 15, wherein the device comprises between three and sevenradially extending occlusion regions, whereby the device includesbetween two and four peripheral edges per centimeter of the axiallength.
 17. A device for occluding a bodily lumen defined by anendoluminal wall, the device comprising: a mesh structure having alongitudinal axis between a proximal end and a distal end, the meshstructure comprising a braided filamentous mesh extending between theproximal end and the distal end, the mesh comprising a plurality ofbraided filaments, each of which terminates at the proximal end in aproximal hub and at the distal end in a distal hub; wherein the meshstructure has a radially compressed configuration and a relaxedconfiguration; wherein the mesh structure in the radially compressedconfiguration has an outside diameter not exceeding 0.7 mm for deliveryto a target site in the bodily lumen; and wherein the mesh structure inthe relaxed configuration has a plurality of radially extendingocclusion regions, wherein each radially extending occlusion region hasa proximal side and a distal side that meet at a peripheral edge,wherein at least one of the proximal side and the distal side forms afirst angle relative to the longitudinal axis of the mesh structure whenin the relaxed configuration, and a second angle less than the firstangle when the mesh structure is radially constrained by contact betweenthe peripheral edge and the endoluminal wall.
 18. The device of claim17, wherein the mesh structure is a single layer continuous braidedstructure.
 19. The device of claim 17, wherein the mesh structure in therelaxed configuration has at least three radially-extending occlusionregions.
 20. The device of claim 17, wherein the first angle is betweenabout 70° and 85°, and the second angle is less than about 70°.
 21. Thedevice of claim 17, wherein the mesh structure assumes apartially-expanded constrained configuration when in the bodily lumen,whereby, in the constrained configuration, each radially extendingocclusion region defines two radial traverses of the lumen for eachfilament, wherein the total number of radial traverses is between 720and
 2000. 22. The device of claim 17, wherein the mesh structure definesan axial length along the longitudinal axis, and wherein the occlusionregions provide between 4 and 10 mesh layers per centimeter of the axiallength.
 23. The device of claim 17, wherein the peripheral edge of eachof the occlusion regions has a thickness of not more than about 2 mm.24. The device of claim 23, wherein the device has an axial length alongthe longitudinal axis, and wherein the device comprises between threeand seven radially extending occlusion regions, whereby the deviceincludes between three and seven peripheral edges per centimeter of theaxial length.
 25. A method for occluding a blood vessel, comprising thesteps of: (a) providing a catheter dimensioned to be introducedintravascularly to a target vascular site; the catheter having a lumenbetween a distal open end and a proximal open end; (b) providing anocclusion device having a longitudinal axis between a proximal deviceend and a distal device end, the occlusion device comprising a braidedfilament mesh extending between the proximal device end and the distaldevice end, the filaments terminating at the proximal device end in aproximal hub and at the distal device end in a distal hub, wherein theocclusion device has a relaxed configuration in which the occlusiondevice has a plurality of radially-extending occlusion regions, whereineach radially-extending occlusion region has a proximal side and adistal side that meet at a peripheral edge; (c) advancing the catheterintravascularly to position its distal open end in or near the targetvascular site; (d) advancing the occlusion device, in aradially-compressed configuration, distally through the lumen of thecatheter until the occlusion device emerges from the open distal end ofthe catheter for deployment in the target vascular site; (e) allowingthe occlusion device to expand radially at the target vascular siteuntil the peripheral edge of each radially-extending occlusion regionengages an endoluminal surface of the target vascular site, wherein whenthe occlusion device is deployed, each radially extending occlusionregion defines two radial traverses of the lumen for each filament,wherein the total number of radial filament traverses is between 720 and2000; and (f) maintaining the occlusion device in the target vascularsite at least until the target vascular site is embolized to occludeblood flow through the target vascular site.
 26. The method of claim 25,wherein the occlusion device is a single layer continuous braidedstructure.
 27. The method of claim 25, wherein the braided filament meshhas a pick angle of at least 40°.
 28. The method of claim 25, whereinthe occlusion device has a maximum relaxed configuration diameter thatis over-sized relative to the diameter of the lumen of the catheter bybetween about 10% and 150%.
 29. The method of claim 25, wherein theocclusion device defines an axial length along the longitudinal axis,and wherein the occlusion regions provide between 4 and 10 mesh layersper centimeter of the axial length.
 30. The method of claim 25, whereinthe occlusion device, when deployed in the bodily lumen, defines anocclusion zone in the lumen between the peripheral edge of a most distalone of the occlusion regions and the peripheral edge of a most proximalone of the occlusion regions, the occlusion zone defining a surface areawithin the lumen, wherein the peripheral edges of the occlusion regionscontact less than about 25% of the surface area defined by the occlusionzone.